1. Field of the Disclosure
The present disclosure relates to a torque sensor.
2. Discussion of the Related Art
In a conventional vehicle, a steering wheel connected to wheels is operated to manipulate a traveling direction of the vehicle. However, an operating force may decrease to make it difficult to quickly operate the vehicle, in case there is a large resistance between wheels and road surface, or there is generated an obstacle to the steering operation. In order to solve the problem, a power steering system is proposed. The power steering system serves to provide a power transfer device to operation of the steering wheels, thereby reducing operating force.
In order for the power steering system to provide a force of operating the steering wheels, needs arise to measure a torque applied to a steering axis, a steering angel and an angular velocity. Apparatus of various methods are proposed for measuring torques of steering wheel. Particularly, a method for detecting a torque is largely employed for economic reasons in which a magnetic field of a magnet coupled to a steering axis is measured to detect the torque.
A steering structure generally includes an input shaft coupled to a steering wheel, an output shaft coupled to a pinion meshed to a rack bar of wheel side, and a torsion bar connecting the input shaft to the output shaft.
In case a steering wheel is rotated, a rotational force is transmitted to the output shaft to change wheel directions responsive to operation of pinion and rack bar. In this case, if resistance is great, the input shaft is further rotated to twist the torsion bar, where a twist level of torsion bar is measured by a torque sensor of magnetic field method.
FIG. 1 is a perspective view illustrating a torque sensor according to prior art. A magnet (10) is coupled to an input shaft, where the magnet (10) takes the shape of a ring. An output is arranged with stators (20, 30), which in turn include vertical lug pieces (21, 31) discretely arranged on a periphery of the magnet (10) and axially bent.
In a case a torsion bar is generated with a twist by a rotational difference between an input shaft coupled to the magnet (10) and an output shaft coupled to stators (20, 30), magnet (10) is rotated relative to the stators (20, 30), where an opposite surface between a periphery of the magnet (10) and lug pieces (21, 31) is changed to change a magnetic value, whereby a torque can be measured.
A collector (40) is arranged to collect the magnetization value and a magnetic element (50) detects the magnetization value collected by the collector (40). Meantime, there is a limit in obtaining an area capable of magnetizing the stators (20, 30) under this arrangement, and thus there is generated a disadvantage of a weak torque signal, that is, a weak magnetic signal. As a result, there is generated a disadvantage of adding a separate process for preparing bent surfaces of stators (20, 30), and arranging the collector (40), whereby structure is complicated to decrease a magnetic detection efficiency.
Another disadvantage under this structure is that it is difficult to bend and arrange the lugs (21, 31) opposite to the magnet (10) in equal dimensions and shapes because a gap between the lug pieces (21, 31) must be equally maintained and it is also difficult to accurately arrange the lug pieces (21, 31).